What happened
On April 4, 2009, a DG-1000T glider with a retractable engine departed from the Boberg airfield via winch launch. The flight, which included a 66-year-old pilot and a student passenger, was intended to be a local sightseeing flight under good visual meteorological conditions. After reaching an initial altitude of 440 meters, the pilot performed several circuits in the southwestern pattern area. During the flight, the pilot utilized the auxiliary engine on two occasions to extend the duration of the flight.
As the flight progressed, the aircraft's altitude steadily decreased. After completing two additional full circles, the aircraft reached an altitude of approximately 125 meters. As the pilot initiated a left-hand turn to enter the final approach for runway 30, the aircraft was observed by witnesses to be flying a flat, shallow turn at a notably low speed. During this maneuver, the aircraft lost lift and entered a stall, pitching forward sharply. The glider struck a fallow field located approximately 150 meters east of the airfield with a high longitudinal pitch. The impact destroyed the cockpit area and caused the fuselage to buckle near the retractable engine mechanism, while the right wing was destroyed halfway up its span.
The investigation
The BFU investigation reconstructed the flight path using data from a carried GPS device. This analysis confirmed that the aircraft had flown two additional circuits, which had reduced the altitude to a level requiring a shortened approach pattern. Investigators examined the aircraft for any mechanical failures but found no technical defects; all structural fractures were determined to be the result of the impact with the ground. The investigation also considered the pilot's experience, noting that while the pilot had sufficient flight hours and experience on this specific model, the low altitude at the time of the maneuver left no margin for recovery.
Findings
- The primary cause of the accident was that the glider was flown at insufficient airspeed during the landing preparations.
- The low airspeed caused the aircraft to enter an aerodynamic stall while executing the turn into the final approach.
- The low altitude at the time of the stall prevented the pilot from successfully recovering the aircraft from the descending flight state.
- There were no technical malfunctions or mechanical failures identified in the aircraft.